Just one little phrase:

"glistening drop of pre-cum"
Once you see that one, it's time to move on.

Other warning signs include:

These are, of course, just some general guidelines. Various subcultures do have their own rules and situations, some of which break the above suggestions (Elf Sternberg comes to mind) and some of which add heavily to these suggestions.

Can you tell I have exacting standards for textporn?

* For reference, he has written better porn than most internet porn. See Bio of a Space Tyrant, Tarot, the later books in the Xanth series, Anthonolgy, any in the Mode series, any in the Incarnations of Imortality series... you get the idea.**
** One does have to wonder, though, if this is a comment on Piers Anthony or a comment on the quality of internet porn.***
*** It's a comment on both. They both suck.